Rewritable portable media such as a USB (Universal Serial Bus) memory have been widely used. A portable medium is connected to a PC (Personal Computer) as a host, is recognized by the PC, and receives a rewrite access from the PC for rewriting data stored in a storage area of the portable medium.
A single portable medium can physically have therein a plurality of storage areas.
Patent Document 1 discloses that a storage area of a mass storage medium is effectively used by logically dividing the storage area into a plurality of divided areas and using a logical unit number for each of a plurality of the divided areas.
Patent Document 2 discloses that an access into an access limit area is limited by conducting authentication for the access.
Patent Document 3 discloses that, if a storage area is not suitable for specifications of an OS (Operating System), the storage area can be hidden.
Patent Documents 4 and 5 disclose that connection of a virtual device in a portable medium is controlled such that a privileged user can use the virtual device but the others cannot.    Patent Document 1: Japanese Laid-Open Patent Application, Publication No. H07-234759    Patent Document 2: Japanese Laid-Open Patent Application, Publication No. H10-289159    Patent Document 3: Japanese Laid-Open Patent Application, Publication No. 2005-115636    Patent Document 4: Japanese Laid-Open Patent Application, Publication No. 2006-202339    Patent Document 5: Japanese Laid-Open Patent Application, Publication No. 2006-286008